After iTunes 11 and Cloud, any custom tagging (e.g. genre, album artist, sort fields) is overwritten resulting in a lack of library integrity.

It also appears that iTunes communicates with the store when copying my albums onto my iPod and uses the store tagging, once again resulting in lost integrity of my library filing structure. Very annoying.

I deleted my personal data using mp3 Tag extended fields option but I am interested in total removal of personal details from my purchases for the above reason - library integrity.